Patent GB-264184-A (GB)
Title: Improvements in and relating to systems of electric distribution
IPC: H02H3/00
Filed: 1927-01-10
Abstract: 264,184. British Thomson-Houston Co., Ltd., (Assignees of Bany, H.). Jan. 8, 1926, [Convention date]. Regulation, automatic; running generators in parallel; synchronizing dynamo-electric machines; systems depending on two or more machines.-A generator 4 supplying a circuit 1 in parallel with other generators and driven by an A.C. motor 3 has its field rheostat 10 operated by a pilot motor 1 normally under the control of a voltage relay 20, but upon reverse current flow through the generator as relay 24 supersedes the action of the relay 20 and decreases the resistance 10, unless the reverse current is due to failure of the A.C. supply 2, whereupon a relay 40 prevents any operation of the rheostat 10 and converts the generator to a compound wound machine, also, upon excess load a relay 29 causes the resistance 10 to be increased. At starting, the machine 3 is run as a squirrel cage induction motor, when the A.C. voltage is normal a relay 52 closes, and when the speed is sufficient a centrifugal relay 56 closes thereby completing a circuit through normally closed contacts 46 for a relay 49 which thereupon completes the field circuit 7 of the motor 3. The generator 4 constitutes a suitable source of supply for the field 7 and the relay 49. When the voltage of the generator 4 is sufficient, the circuitbreaker 8 is closed and therewith contacts 48 which complete a circuit from one of the feeders to the various relays, these thereupon becoming operative. During normal operation, if low voltage occurs at some load centre to which the voltage relay 20 is connected, this relay closes its lower contacts and completes a circuit from contacts 48 through normally closed contacts 47, 32 to a relay 14 which closes to cause the pilot motor to decrease the resistance 10. High voltage causes the relay 20 to close its upper contacts. completing a circuit from contacts 48 through normally closed contacts 47 and 27 to a relay 17 which closes to cause the pilot motor to increase the resistance 10. Reverse current in a shunt 28 causes the relay 24 to open its contacts 27 thereby preventing actuation of the relay 17, and closes contacts 26, thereby energizing relays 33, 36. Relay 33 completes a circuit from contacts 48 through contacts 47 to the relay 14 and thereby decreases the resistance 10, and relay 36 removes a short circuit from a differential series field 6, so that the machine 4 runs as a compound wound motor. If the reverse current is due to failure of the A.C. supply 2, relay 40 drops and energizes relay 44 which opens its contacts 46 to de-energize relay 49 and therefore the field 7, and also opens its contacts 47 so as to prevent action of either of the relays 14. 17. In this case, the series field 6 stabilizes the speed of the set 3. 4 and prepares the motor for resynchronization upon restoration of the A.C. supply. Excess current in the shunt 28 causes the relay 29 to open its contacts 32 to prevent the relay 20 from operating the relay 14, and to close its contacts 31 to cause operation of relay 17 subject to the contacts 27 being closed.